A dihydropyridine derivative of the formula (I) ##STR2## wherein each symbol is as defined later, has a calcium channel antagonistic action and is already known to be useful as an hypotensive agent, a cerebral vasodilating agent and a therapeutic agent for coronary artery disorders (therapeutic agent for angina pectoris) (Japanese Patent Unexamined Publication No. 225356/1988, U.S. Pat. No. 4,886,819, EP-A-257616).
It has been also known that the above-mentioned derivative (I) is extremely useful as a cerebral blood flow increasing agent (Japanese Patent Unexamined Publication No. 62824/1990, EP-A-342577), a therapeutic agent for vasospasm (Japanese Patent Unexamined Publication No. 180826/1990, EP-A-379737) and a heart stimulant (Japanese Patent Unexamined Publication No. 235168/1992, EP-A-463407).